<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /*
      并集选择器
       ● 选择器之间用 , 分隔
       ● 满足其中一个选择器的条件
     */
    p,
    #red,
    .red {
      color: red;
    }
  </style>
</head>

<body>
  <p>Hello world!</p>
  <div id="red">Hello world!</div>
  <div class="red">Hello world!</div>
</body>

</html>